Limits to Sustainability, Population, and the TEDx Experience

A recent TEDx talk delves into our species’ reverence for economic and population growth, which is pushing us – and the natural world – outside our safe operating space. In ‘Limits to Sustainability’, João Abegão attempts to communicate the expanding footprint of our species by comparing it with transformations suffered by past complex societies.

By João Abegão

TEDx talk ‘Limits to Sustainability: Lessons from the Past and New Imaginaries’. Photography and video by Filipe Silva Studio/TEDxAlcobaça. Click the image to view João Abegão’s TEDx talk, English subtitles begin at 1:15 min.

It has now been about five years since I have started walking down the academic trail. From the start, I knew that I wanted to address human overpopulation, so I took it as my master’s dissertation to extensively read, compile and draft what ended up being the Human Overpopulation Atlas. Since then, I have attempted to normalize the communication of this hot topic by featuring in different podcasts and conferences or by the written medium through scientific papers and essays (one such already for TOP).

After a panel participation on human overpopulation at the last COP, I decided to embrace a new challenge to reach a wider audience with this topic. An opportunity presented itself when I was invited to talk about sustainability to the giants of communication, TEDx (x stands for a grassroots movement at the level of local communities). After some back and forth with the organization, I decided that the talk would be called ‘Limits to Sustainability: Lessons from the Past and New Imaginaries‘.

This talk picks up from the work I’m currently developing for my doctoral thesis. It is centred on the notion that increasingly noticeable limits are being breached by an inflated human enterprise (consisting of both the growth of the human population and economic activity), ultimately setting this modern, industrial, and highly complex civilization (hereafter, civilizational project) on a path to collapse. To understand the unsettling prospect of collapse, I have turned to the fields of environmental history, palaeoclimatology, and archaeology. I hope that through the interpretation of how past complex societies were faced with climatic shifts or the anthropogenic degradation of their environments, we might be better equipped to grasp the unprecedented predicament we find ourselves in.

The talk revolves around the notion that humanity is driving unprecedented planetary change and that such a transformation can be detected by increasingly noticeable socio-economic and environmental trends. The now influential framework of ‘planetary boundaries’ captures these trends. Since the mission of TED is to bring ideas worth spreading to general audiences, there was a need to break down this complex topic into a narrative fashion. I did this by resorting to an incident with my garden pond, which made me realize that the small, confined, exposed pond was a metaphor for our besieged planet.

Circling this back to overpopulation, one of the main inferences deriving from my thesis (and this talk) is that if past levels of population and per capita demands – which were far smaller than today – were capable of causing discernible environmental degradation and overshoot in past complex societies, it follows that our bloated human enterprise will likely beget a transformation of the planet so profound that it can only be compared to the futuristic ‘Muskian’ reveries of terraforming Mars – only in reverse.

In a way, what I have set myself to study is the ecocide thesis popularized by Jared Diamond in his acclaimed book Collapse: How Societies Choose to Fail or Succeed (2005). Diamond’s work is far from being alone in arguing that population growth and creeping environmental degradation would have adversely affected past complex societies. In fact, a trove of popular and academic works exists on the subject.

The problem is that arguing for the contribution of climate and anthropogenic exploitation as significant drivers of change in the past does not have a spotless record in academia. I won’t bore you all with the tribulations of the field, but to sum up, upholding the influence of such drivers continues to invite accusations of environmental and climate determinism: that societies such as the Western Roman Empire or the Mayans were the victims of external climate influence or mindless degradation of their surroundings and that such factors were the sole and ultimate cause of their demise. Push-back against environmental determinism deterred scholars from examining how such environmental changes have influenced historical events for over half a century. They are only recently resuming that work. Of course, the implications of population growth were also neglected in the process.

A predictable consequence of this oversight is that we are faced with a delay of several decades of research on the implications of climate and overshoot in driving the transformation and collapse of past societies. Hence, researchers such as the archaeologist Joseph Tainter have claimed (2006, p. 71) that “there does not presently appear to be a confirmed archaeological case of overshoot, resource degradation, and collapse brought on by overpopulation and/or mass consumption.”

One important part of science is criticism, and repeated evaluation of colleagues’ ideas and work. Environmental historians, archaeologists, and paleoclimatologists should take a close look at the works of Tainter and others. A recent example comes from Lima and colleagues (2020), who have set out to study the feedback mechanisms that operated between climate, demography and ecological factors on Easter Island (Rapa Nui), that led to the overshoot of its carrying capacity, eventually contributing to widespread societal collapse.

I was asked to come up with a message that would end on a positive note, even though the central theme of my talk was quite pessimistic/realistic. Considering that I loathe those mandatory ‘feel-good’ messages like “CO2 emissions continue to rise at a rapid pace, but there is still hope”, or “extinction rates are so elevated that they can only be compared to major mass extinction events… but here is a list of 5 things you can do to help” (that won’t include not having children), I wasn’t about to sell my soul, so I told the audience:

Despite decades of treaties, conferences and appeals to change, CO2 concentrations do not stop rising. Why? Because to reverse this tendency, it would be required not just to stop growing the economy and the population, but to contract both of them.

This is it! Present-day levels of the economy and the global population will never allow a sustainable permanence of our species on this planet. And when we realize that both these factors are foreseen to keep expanding in the future – until at least the planetary boundaries prevent such a thing – CO2 concentrations will undoubtedly keep on increasing.

I ended up researching and asking people what approaches they considered to have a genuinely positive impact still. With the short time I had left, I urged the audience to generally:

Protect natural areas and their inhabitants, and don’t allow illusions of progress to destroy them. Cooperate with initiatives centred around conservation, rewilding, reforestation, restoration, and clean-up campaigns. The removal of dams also does wonders for ecosystems. Seek to understand better the concepts of steady-state and degrowth economies and support politicians who are willing to endorse them. Uphold access to quality education, for both boys and girls worldwide, as well as access to contraceptive methods, the right for women and girls to decide what to do with their bodies, and of course, do not be afraid to promote a small-family model of a single child.

While on the level of the individual, at least on what concerns contributions to climate change, I suggested:

To use your car as little as possible, reduce the consumption of animal products, to avoid air travel, and of course, to opt for a smaller family size, not having, preferably, more than one child, and adopting whenever possible.

I concluded my talk by alluding to the concept of ‘wicked problems’ that are now so profoundly intertwined that when we try to deal with one, we end up aggravating others. I resorted to the excellent infographic from Michele Guieu for the Millennium Alliance for Humanity and the Biosphere (MAHB) that depicts our ‘Human Predicament’.

My closing remarks were meant to illustrate the immense uncertainty that is associated with the planetary experience that we are conducting while dismissing the recurring need for messages of ‘hopium’ that generally characterize these talks:

I would like to end and say that if we did everything as I just outlined, that both humanity and the living world could mutually prosper for a long time, but we just don’t know if it is possible…

But what I do know is that as long as we glorify the growth of both the population and the economy, while we maintain a culture that requires industrial levels of energy and resources to operate, every limit mentioned here, and others, will invariably be surpassed. Our species might survive, but we will lose the harmonious climate reality that we still revel in, simultaneously driving to extinction many other species as we convert and homogenize this planet for our ends.

These are the consequences of our unsustainability.

Outside I was met by an audience member who told me that she did not agree with everything I had said, but had nothing but absolute respect for those committed to communicating complex subjects. The TEDx talk is done, but the work of dissemination starts now. If you are among the people that care about the issues outlined here, and you think that these are ‘ideas worth spreading’ (even if disagreements exist), I can only invite you to share the video and get it circulating among the masses and critical players. That’s how we can tap into the potential of these projects.


João Abegão’s TEDx talk is available here, English subtitles start at 1:15.

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9 thoughts on “Limits to Sustainability, Population, and the TEDx Experience

  1. Excellent effort but lacking in immediacy and personalization. So, if we keep turning out 206,000 new copies of ourselves daily, exhausting natural resources, and polluting the planet, we are certain to become sicker form all of the “diseases of civilization” (none of which are to be found among traditional clan-living Hunter-Gatherers) and destroy the 1-3% of the “wild” land-based vertebrates barely surviving today. I have written a free e-book, “Stress R Us”, available at, and giving 623 pages of hard evidence to support my contention that “population density stress is killing us NOW!”. BTW, we reached Earth Overshoot day this past July, 29th. As little Greta all but said in her Glasgow rally, until we confront Capitalism as the driving economic force further driving pronatal and progrowth corporate agendas, nothing will change and Titanic Earth will just continue to flood and sink to the bottom of our ever warmer ocean. Stress R Us

  2. There is much scientific and demographic research literature of the past generation to show we are facing population decline by mid century and afterwards.

    This dynamic is evidenced by already below replacement fertility rates and increasing dependency ratios i.e. more pensioners and proportionately fewer taxpayers of working age to support budgets, to pay pensions…..

    After mid century population will rebalance, especially giving young more voice, after our high fertility generations have passed. Interestingly the UNPD, whose data analysis is used to inform Worldometers etc., has not got the memo yet….

    1. The population is too high NOW and will increase to 2050! And political actions are not sufficiently strong!

    2. The projection of population decline applies only to the richer countries with high levels of health and family planning provision. This is where the double standard comes in. Millions of people living in povetry have neither wealth nor safe and effective family planning. So the worlds are increasingly diverging.

  3. Excellent performance and efforts! Thank you so much joao! 😀🎈👍😊Many understand most of your message! But overpopulation should be stronger stressed as so many neglect it and think it is enough population growth stops 2060!!! Its not just about female rights and goes deeper than family planning! Make the impact larger on the most important – and often neglected – aspect!!!!

  4. “Seek to understand better the concepts of steady-state and degrowth economies and support politicians who are willing to endorse them”
    There aren’t any.

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